1. Field of the Invention
The present invention is directed to a conveyor shaft seal and relates more particularly to an inexpensive and efficient bearing seal apparatus for preventing discharge of material into the shaft bearing.
2. The Prior Art
It is known to provide sealed shaft bearings for conveyors which employ as the sealing means a packing surrounding the shaft. In accordance with such devices the packing is compressed about the shaft by an annular insert adapted to be shifted longitudinally of the shaft and, since the packing is constrained in an annular cavity, such axial movement causes the packing to embrace the shaft.
Packing type seals have known disadvantages, including particularly the necessity for frequent adjustment to assure intimate pressure of the packing about the shaft. In addition, the packing exerts a high frictional drag, must be frequently replaced, and often results in scoring of the shaft.
A particular disadvantage of packing type seals resides in their inability to accommodate any significant eccentricities of the shaft.
In my U.S. Pat. Nos. 3,988,026 and 4,365,707 there are described improvements in conveyor shaft seals wherein the disadvantages of packing are obviated, the seals exhibiting protracted operating life and ability to accommodate significant shaft eccentricities . The seals of the noted patents, while having achieved substantial commercial success, are relatively expensive.
In accordance with a further known shaft seal apparatus there is provided a bearing member which embraces the shaft, the bearing being supported within a surrounding frame of elastomeric material. By so supporting the bearing a substantial amount of eccentricity of the shaft may be accommodated.
However, bearing seals of the last mentioned type have the disadvantage that material in the conveyor, particularly if it is finely divided and abrasive, rapidly enters the interface between shaft and bearing and compromises the seal therebetween.